Don't forget 2 strokes will run hot with excessive shaft load, so when you then put that in a pusher setup you have potential for a temperamental arrangement. So if this is a Cox .049, I'm not a fan of that 6-4 (even in a tractor setup. Let 'em spin, keep 'em cool and happy - 5-3 good prop. I'm not saying it is a disaster waiting to happen, just not a direction I would be comfortable with.
If it is something else.. then what is it rcdf?